Hello Abdullah,

Please correct me if I am wrong in understanding your question. You want to know what WebGrid Filter mechanism or WebGrid does, when select an FilterItem from FilterContextMenu, correct?
If yes, I would need to discuss with our developer to ensure the details.

Regards,
Handy

Which code do you use to show the filterbar in grid.

Is it only grid.ShowFilterBar()? because I found the grid row display area autometically get resized then l click filterbar from ConextMenu.

Another problem: Is there any flag which can give us information that the filterbar is currently visible or invisible?  

Hello,

Yes. To show FilterBar, you need to use grid.ShowFilterBar(). Vice versa, To hide FilterBar, use grid.HideFilterBar(). The display area is automatically resized.
Actually, it only hide the element of FilterBar.
If you would like to know how it works, you can try to see the following code.

function Hide_onclick() 
{
            var grid = ISGetObject("WebGrid1");
            grid.HideFilterBar();
            alert(grid.RootTable.GetFilterRow().style.display);
}
function Show_onclick() 
{
            var grid = ISGetObject("WebGrid1");
            grid.ShowFilterBar();
            alert(grid.RootTable.GetFilterRow().style.display);
}

When hide the filter bar, it uses style display none. Vice versa, it uses style display " " to show the filter bar. Maybe you can use this as the flag.

Regards,
Handy